1. Field of the Invention
The present invention relates to expanding bit resolution, and more particularly to expanding the bit resolution of a pixel depending on different threshold values using the local characteristics of an image, thus improving the quality of the image without causing the loss of a texture or pattern, and recovering a lost image.
2. Description of the Related Art
Generally, in image processing, lower bits of a pixel value are discarded in a quantization procedure. This results in reduced image quality, or in artificial contours being generated between the components of the image.
In order to solve these problems, research on the expansion of bit resolution has been carried out. U.S. Pat. No. 5,907,370 discloses a method of comparing the difference between a resultant value obtained from low pass filtering, and a resultant value obtained from bit shifting using a predetermined threshold value, and determining an output value, as a method of expanding bit resolution.
However, such a method is problematic. Since a single fixed threshold value is applied to an entire image, low pass filtering is uniformly applied to the entire image without consideration of the local characteristics of the image. As a result, blurring may occur in a portion of the image in which a texture or pattern exists.